Compressor machine with two counter-rotating rotors

ABSTRACT

The compressor machine has two rotors rotating in opposite directions, which are fitted to two parallel, spaced apart shafts mounted in a housing. One of the shafts is driven directly and the other by intermeshing toothed gears mounted on the shafts. The housing has two radial walls which are configured in one piece with each other and with a peripheral wall and in which the shafts are mounted. The toothed gears are arranged between these radial walls. A side wall of the housing has an opening sealed by a removable cover. With the cover removed, the toothed gears can be fitted to the shafts through these openings. The bearing bores for the shafts can be produced and machined in the one-piece housing in a single set-up, so that, with a minimum number of parts, any causes of alignment errors are avoided.

FIELD OF INVENTION

The present invention relates to a compressor machine comprising tworotors rotating in opposite directions, which are fitted to twoparallel, spaced apart shafts mounted in a housing, one of the shaftsbeing driven directly and the other by intermeshing toothed gearsmounted on the shafts.

BACKGROUND OF THE INVENTION

Compressor machines with two rotors rotating in opposite directions canoperate as compressors or vacuum pumps. EP 1 163 450 A1 discloses amachine of this type, having claw-type rotor blades, which is adapted togenerate both suction air and blown air and is particularly suitable foruse in the field of paper processing. The internal compression ofmachines of this type allows to attain markedly higher pressure ratiosthan for instance by means of a Roots pump. The cantilevered arrangementof the rotors in a pot-shaped housing results in a simple structure.However, the gear that couples the two shafts, on the one hand, and theshaft mounting, on the other hand, are disposed in separate housingparts which need to be exactly aligned with each other and pinnedtogether. Similarly, the pot-shaped housing accommodating the rotorsneeds to be precisely pinned together with the gear casing. This resultsin the requirement of having to machine pin holes from two differentsides of a housing part as precisely as possible. Any imprecision willlead to slanting shafts and thereby to increased bearing loads, toothedgear noises, and other malfunctions.

SUMMARY OF THE INVENTION

The invention provides a compressor machine which ensures a preciseorientation of the shafts in spite of a simplified manufacturing and areduced number of parts.

The compressor machine according to the invention comprises a housing,two parallel, spaced apart shafts mounted in the housing, intermeshingtoothed gears mounted on the shafts, one of the shafts being drivendirectly and the other by said intermeshing toothed gears and two rotorsrotating in opposite directions, which are fitted to the two parallel,spaced apart shafts. The housing further includes axial passages, tworadial walls which are configured in one piece with each other and witha peripheral wall and in which the shafts are mounted and between whichthe toothed gears are arranged. One of the radial walls is a radialouter wall and the other is an intermediate wall which on one sidethereof defines together with the radial outer wall a gear chamberreceiving the toothed gears and on the other side thereof defines aworking chamber receiving the rotors. On an end-face facing away fromthe intermediate wall, the working chamber is sealed by a radial housingcover. The intermediate wall has axial through openings foraccommodating shaft bearings having a width larger than that of theaxial bearing bores in the radial outer wall. The housing furthercomprises a side wall having an opening sealed by a removable lateralcover. Furthermore, the housing constitutes a monobloc base body thathas an opening at an end-face facing the housing cover, said openinghaving a width that is the largest among said axial passages and boreholes located inside the housing, making them accessible for machiningthrough this opening in one set-up of the base body.

With the cover removed, the toothed gears can be fitted to the shaftsthrough these openings. The bearing bores for the shafts can be producedand machined in the one-piece housing in a single set-up, so that, witha minimum number of parts involved, any causes of alignment errors areavoided. The cover sealing the opening in the side wall of the housingdoes not in any way affect the mounting of the shafts. The cover is asimple part which is merely required to close the opening and seal itagainst any escape of oil. It has turned out that this allows theavoidance of even minor positional inaccuracies, resulting in animproved efficiency and reduced running noises.

Further features and advantages of the invention will be apparent fromthe following description of a preferred embodiment and from theaccompanying drawings, in which:

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 shows a side view of a compressor machine;

FIG. 2 shows an axial section of the compressor machine;

FIG. 3 shows a perspective view of a one-piece housing body of thecompressor machine;

FIG. 4 shows three sketches to illustrate an internal compression;

FIG. 5 shows an enlarged detail view of a shaft seal; and

FIG. 6 shows an axial section of an alternative embodiment of thecompressor machine.

DETAILED DESCRIPTION OF THE INVENTION

The compressor machine described by way of example below includes rotorshaving claw-type rotor blades and may be operated both as a compressorand as a vacuum pump.

A pedestal 10 mounts an integral housing body 12 having a flange-mountedelectric motor 14. The housing body 12 has two radial, parallel andspaced apart walls 16, 18 connected with each other by a peripheral wall20. The radial wall 16 forms an outer wall. The radial wall 18 forms anintermediate wall of the housing body 12 and separates a gear chamber 22formed between the walls 16, 18 from a working chamber 24 which receivesa pair of rotors 26, 28 having claw-type rotor blades. The rotor 26 iscantilever-mounted at an axial end of a shaft 30 which is supported inthe radial walls 16, 18. The opposite axial end of the shaft 30 isdirectly coupled to the output shaft of the electric motor 14. The rotor28 is cantilever-mounted at an axial end of a second shaft 32 which islikewise supported in the radial walls 16, 18. The shafts 30, 32 areparallel and spaced apart from each other. The shafts 30, 32 are coupledwith each other by two intermeshing toothed gears 34, 36 arranged in thegear chamber 22, so that they rotate synchronously and with oppositesense of rotation.

The housing body 12 has a side wall with an opening 38 that can beclosed off by a cover 40 fitted from outside. This opening 38 isdimensioned such that, with the cover 40 removed, the toothed gears 34,36 can be inserted into the gear chamber 22 for installation on theshafts 30, 32.

On the side of the working chamber 24, a bearing cover plate 42 isapplied to the intermediate wall 18. At its axial end facing away fromthe bearing cover plate 42, the working chamber 24 is closed off by aradial housing cover 44. The housing cover 44 is adjoined by a hood 46which encompasses a fan that is coupled with the shaft 30, for example,or is provided with an external drive.

The compressor machine described preferably involves a so-calledclaw-type compressor, that is, a machine with claw-shaped rotor bladesand with an internal compression. FIG. 4 shows three phases in the cycleof such a machine, more specifically, in a) the beginning of thecompression process, in b) the compression process at an advanced stage,and in c) the phase of expulsion of the compressed volume. The phaseshown in FIG. 4 a) is preceded by the inlet phase, in which a sharedinlet chamber is filled, then divided up into two partial chambers, andfinally combined into a joint volume, which then experiences theinternal compression. An outlet port denoted by A is closed by one ofthe end faces of the lower rotor upon rotation of the rotors during thephase of internal compression and during the inlet phase. Starting withthe condition illustrated in FIG. 4 b), the outlet port A is exposed bythe lower rotor to allow the compressed volume to be expulsed via theoutlet port A. This outlet port leads axially through the housing cover44 out of the working chamber of the compressor machine.

FIG. 5 shows an enlarged illustration of the shaft mounting at theintermediate wall 18 and the shaft seal arranged at the bearing coverplate 42. The shaft mounting consists of a double ball bearing generallydenoted by 50. A recess 52 is formed in the bearing cover plate 42 toreceive the shaft seal. Arranged in the recess 52 is a shaft sealingring 54 which is made of a rubber elastic material and has a pointedsealing edge 54 a which is in sealing engagement with the outerperiphery of a sleeve 56 shrunk on the shaft 32. The sleeve 56 is sealedfrom the shaft 32 by a sealing ring 58. The sleeve 56 has a radiallyraised shoulder 56a having two sealing rings 60 received therein axiallynext to each other. The sealing rings 60 serve to seal the sleeve 56from the inner periphery of the recess in the bearing cover plate 42.Remaining between the sealing ring 54 and the recess in the bearingcover plate 42 is a space 62 which communicates with a bore hole 64. Thebore hole 64 leads through the bearing cover plate 42 and to theoutside.

The special feature of the shaft seal illustrated in FIG. 5 consists inthat it is arranged at the bearing cover plate 42, in this way allowingan unproblematic installation from the open end face of the base body ofthe housing.

In the embodiment of the compressor machine shown in FIG. 6, the basebody of the housing is surrounded by a hood 70 defining axial coolingair ducts 72 together with the outer periphery of the housing. Thecooling air ducts 72 extend from a protective grille 74 next to thehousing cover 44 axially along the outer periphery of the housing as faras behind the gear chamber where they open radially inward into a fanchamber 76 having a fan arranged therein that has a rotor which issecured on a driving shaft coupled to the lower shaft 30. The coolingair exits radially downward.

For exemplification, it should be noted that the shafts are in axialpassages 100 a, 100 a′, 100 b, 100 b′. The passages include the axialbearing bores 100 b, 100 b′ in the radical outer wall. The passages alsoinclude openings 100 a, 100 a′ in the intermediate wall. Also, the fan103 includes hood 70 as a covering.

1. A compressor machine, comprising: a housing; two parallel, spacedapart shafts mounted in the housing; intermeshing toothed gears mountedon the shafts, one of the shafts being driven directly and the other bysaid intermeshing toothed gears; two rotors rotating in oppositedirections, which are fitted to the two parallel, spaced apart shafts;the housing including axial passages; two radial walls which areconfigured in one piece with each other and with a peripheral wall; theshafts being mounted between the radial walls; the toothed gears beingarranged between the radial walls; one of the radial walls being aradial outer wall and the other an intermediate wall which on one sidethereof defines together with the radial outer wall a gear chamberreceiving the toothed gears and on the other side thereof defines aworking chamber receiving the rotors; on an end-face facing away fromthe intermediate wall, the working chamber is sealed by a radial housingcover; the intermediate wall has axial through openings foraccommodating shaft bearings having a width larger than that of theaxial bearing bores in the radial outer wall; a side wall having anopening sealed by a removable lateral cover; the housing constituting amonobloc base body that has an opening at an end face facing the housingcover, said opening having a width that is the largest among said axialpassages and bore holes located inside the housing, making themaccessible for machining though this opening in one set-up of the basebody.
 2. The compressor machine according to claim 1, wherein the rotorsare cantilever-mounted on the shafts.
 3. The compressor machineaccording to claim 1, wherein on the end face facing away from theintermediate wall, the working chamber is sealed by a housing coverhaving an outlet port formed therein which upon rotation of the rotorsis exposed subsequent to a phase of internal compression and is closedby the end face of one of the rotors during an inlet phase.
 4. Thecompressor machine according to claim 1, wherein a bearing cover plateis applied to the intermediate wall on the side of the rotors.
 5. Thecompressor machine according to claim 4, wherein the bearing cover platehas recesses for receiving shaft seals.
 6. The compressor machineaccording to claim 1, wherein connected to the radial housing cover is ahood enclosing a fan.
 7. The compressor machine according to claim 1,wherein the peripheral wall of the housing is surrounded by a hooddefining axial cooling air ducts together with the peripheral wall, thecooling air ducts extending from the end face adjacent to the housingcover up to a fan arranged on a driving shaft on the side of the gearchamber facing away from the working chamber.